The present invention relates to a trimming tool and, more particularly, to a combination string and blade trimmer including an auxiliary blower function.
A trimming tool is typically used for cutting vegetation such as grass and the like using one or more strings secured to a string spool assembly that is rapidly rotatably driven by a motor. U.S. Pat. No. 5,063,673 describes one type of string spool housing that incorporates an automatic string feed mechanism that utilizes centrifugal force to sense a string breakage. GB2 000 672 describes a grass cutting attachment for a rotary machine such as an electrically operated drill. A blade trimmer operates on the same principle as a string trimmer, but uses one or more blades in place of the string. DE 25 56 553 discloses a cutter head that includes blades. Blades normally do a better cutting job than string, but blades cannot be used against a curb or hard surface.
It is thus desirable to provide a trimming tool that can be selectively used in a string trimming mode and a blade trimming mode. Previously, in order to convert a string trimming tool to a blade trimming tool, the trimmer head had to be disassembled and reassembled to replace the string spool housing with a blade unit. By the nature of the tool, the disassembly of the trimmer head is inherently a dirty task that most consumers would only perform once and would not bother to repeat.
In addition, clippings resulting from the cutting operation must be raked and collected to improve the overall appearance of the grounds maintenance. U.S. Pat. No. 4,227,280 describes a vacuum/blower attachment that can be mounted to a conventional filament line trimmer. U.S. Pat. No. 4,187,577 describes an attachment device for converting a line trimmer to a blower. U.S. Pat. Nos. 4,835,950 and 4,827,702 show a fan blade attachment that may be attached to the outer periphery of the filament line spool of a filament line trimmer. It would thus also be desirable to incorporate a blower function with the trimming tool to facilitate collection and removal of clippings from the cutting operation.
The combination string and blade trimming tool according to the present invention enables a quick conversion between a string trimming mode and a blade trimming mode without requiring the user to disassemble and replace a trimmer head. Moreover, a preferred embodiment of the invention also contemplates an auxiliary blower that utilizes airflow generated by operation of the motor to be fluted to an exit opening to effect a blower function. Alternatively, a fan could be provided separately from the motor for increased efficiency.
According to the present invention, a selectable blade assembly attachment is attachable to an existing or slightly modified string trimmer assembly. In one embodiment, one or more trimming blades are pivotally attached to a disc or the like, which in turn engages a string spool housing of the trimmer. The one or more trimming blades are biased toward a retracted position by a spring and are locked in the retracted position by a locking mechanism in a string trimming mode. To convert from the string trimming mode to the blade trimming mode, the motor direction is reversed, releasing the locking mechanism, and the one or more trimming blades are pivoted to an extended position against the force of the spring by centrifugal force. The locking mechanism may be an inertial lock that is activated by centrifugal force. In order to convert back to the string trimming mode, when the motor is stopped, the one or more trimming blades are pivoted toward the retracted position by the spring, and the locking mechanism is engaged when the motor rotates in the string trimming mode direction. With this structure, an operator can readily switch between a string trimming mode and a blade trimming mode without requiring disassembly of the trimming head.
In an alternative arrangement of the invention, the combined functionality can be achieved without requiring reversing of the motor. In this arrangement, a mechanical actuator positioned near the handle of the tool is attached to a rotatable cam plate or the like. When the operator rotates the cam plate, cam surfaces on the cam plate shift a latch pin from a lowered position to a raised position, which in turn displaces a latch from a locking position to a releasing position. In the releasing position, the trimming blade is free to pivot outward by centrifugal force against the force of the spring. When the motor is stopped, if the operator desires to return the tool to the string trimming mode, the trimming blade is returned toward its retracted position by the spring and can be resecured with the latch by again rotating or pulsing the cam plate with the mechanical actuator. Thus, with this structure, the selectable trimming modes can be realized also without requiring disassembly of the trimming head and additionally without requiring an implementation of a reversible motor.
A permanent auxiliary blower capability can be incorporated into the trimming tool according to the invention. In this context, the fan may be separated from or part of the string spool, and a blower scroll is inserted around the fan and under the spool. The scroll is screwed or otherwise secured to the underside of the tool guard. The blower preferably functions continuously with motor cooling air being directed by the blower scroll. Alternatively, an optional air exit cover may be connected by cable or the like to a handle trim/blow selector switch, and in the trim mode, essentially motor cooling air blows into the string or blade plane to act as an air boost; in the blow mode, the cover is full open for mass directed air forward. With the blower functionality, the trimming tool according to the invention incorporates diverse applications and facilitates collection and removal of clippings from the trimming operation.
In accordance with a particular aspect of the present invention, there is provided a selectable blade attachment for string trimming tool including a motor rotatably driving a string spool housing. The selectable blade attachment includes a trimming blade assembly engaging the string spool housing and having at least one trimming blade. The trimming blade is pivotable between a retracted position and an extended position by centrifugal force. The blade attachment preferably further includes a locking mechanism selectively engageable with the trimming blade, wherein in a locked position, the locking mechanism locks the trimming blade in the retracted position. The locking mechanism is preferably structured such that it is reciprocated between the locked position and an unlocked position by centrifugal force. In one arrangement of the invention, the locking mechanism is reciprocated between the locked position and the unlocked position based on a rotation direction of the motor. In preferred forms, the trimming blade is biased toward the retracted position by a spring.
Additionally, the attachment preferably includes a spool lock engageable with the string spool housing in a locking position to prevent automatic string feeding in the blade trimming mode, wherein the spool lock is shifted between a releasing position and the locking position by centrifugal force.
Other features of the invention utilize a locking bar and blade lock plate in the locking mechanism. Structure supporting the blade and locking mechanism may include chamfered edges to decrease wind resistance during operation. In yet another arrangement of the invention, the locking mechanism is engaged and disengaged with an actuator, such as a pull cable.
In accordance with another aspect of the invention, there is provided a trimming tool including a motor having an output shaft, a string spool housing attached to the output shaft for rotation by the motor, wherein the string spool housing spools a cutting string for the tool, and a trimming blade assembly engaging the string spool housing including at least one trimming blade, wherein the trimming blade is pivotable between a retracted position and an extended position by centrifugal force.
In yet another aspect of the invention, there is provided a method of operating a trimming tool in a string trimming mode and a blade trimming mode. The method includes providing a motor having an output shaft, providing a string spool housing attached to the output shaft for rotation by the motor, with the string spool housing spooling a cutting string for the tool, and providing a trimming blade assembly engaging the string spool housing and including at least one trimming blade, with the trimming blade being pivotable between a retracted position and an extended position by centrifugal force. In the string trimming mode, the method includes locking the trimming blade in the retracted position, and rotating the motor with the trimming blade in the retracted position. In the blade trimming mode, the method includes releasing the trimming blade, and rotating the motor so that the trimming blade is pivoted to the extended position by centrifugal force.
The rotating step in the string trimming mode may include the step of rotating the motor in a first direction, and the rotating step in the blade trimming mode may include the step of rotating the motor in a second direction, opposite from the first direction. The method may still further include preventing string spool feeding in the blade trimming mode. In another step, the method includes effecting a blower function using the motor.